Controlling mechanism for electric motors



(No Model.)

L. T. GIBBS. 5 CONTROLLING MECHANISM FOR ELECTRIC MOTORS. I

No. 555,503. Patented Mar. 3, 1896 I awmwdfr 2 m I awe a):

@PWWWW UNITED STATES PATENT OFFICE.

LUOIUS T. GIBBS, OF MILVAUKEE, WISCONSIN,

CONTROLLING MECHANISM FOR ELECTREC'MOTORS.

SPECIFICATION forming part of Letters Patent No. 555,503, dated March 3, 1896.

Application filed January 2, 1896.

To aZZ whom it may concern:

Be it known that I, LUCIUS T. GIBBS, of Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Controlling Mechanism for Electric Motors; and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it pertains to make and use the same, reference being had to the accompanying drawing, and to the letters of reference marked thereon, which forms apart of this specification.

The main object of my invention is to avoid injury to the motor by an abrupt increase of current through the armature, or the sudden closing of the armature-circuit, so as to allow the full current to pass through the armature before it has time to get under motion and generate a counter electromotive force.

It consists of certain novel features in the construction and arrangement of component parts of the controlling devices hereinafter particularly described and pointed out in the claims.

Referring to the drawing, which shows in elevation my improved switch in connection with a shunt-wound electric motor, which with the electric circuits are shown in diagram, A designates the armature and B B the fields of an electric motor. 0 and D are the main wires or conductors by which the motor is supplied with current, and E is a double pole or other suitable switch for main ually opening and closing the main circuit.

0 c is a branch of the main circuit which passes through the armature and may be designated, for convenience, the armature-circuit, and d d is a branch of the main circuit which passes through the fields of the motor and may be designated the field-circuit.

F is a manually-operated switch-lever pivoted upon a pin f in the usual or any suitable way, and g to g are contacts over which the lever F is adapted to sweep and to engage successively, connected with each other by resistance-coils G G and with the armaturecircuit 0 in series.

f. and f are stops for limiting the movement of the switch-lever F in its initial and Serial No. 574,020. (No model.)

final positions, as shown by full and dotted lines. In its initial position, as shown by full lines, the circuit through the armature of the motor is broken, and in its final position, as indicated by dotted lines, the armature-circuit is closed and all of the several resistancecoils are cut out of said circuit, so that the full current passes through the armature. As the lever is turned from its initial to its final position, it first engages the contact g, closing the armature-circuit with the several resistance-coils G G included in circuit. As it passes in succession over the several contacts g to 9 the resistance-coils G G are successively cut out as the armature increases in speed and generates counter electromotive force.

H is a switch-arm made of iron or steel and pivoted on the pin f concentrically with lever F, with which it is in electrical connection, and independently of which it is movable.

K is an electromagnet which has its winding included in the field-circuit cl in series with the field and its core is projecting at one end into the path of the arm H, and constituting a contact-stop therefor. The arm I-I constitutes or carries the armature of said electromagnet and with the lever F serves as a part of the armature-circuit c, the core or pole-piece of the electromagnet being electrically connected with the main wire or conductor D.

71 is a stop arranged to limit the movement of the arm H away from the core of the electromagnet at such a distance therefrom as to be unaffected by the attraction of said magnet when energized by the normal working current.

L is a spiral spring attached at the ends to the lever F and arm H by means of pins or studs I I, which carry it in a position to clear the center pin f when the lever F is turned in either direction past the line of the arm H. The spring L is made of such tension or strength that it will not overcome the attraction of magnet K when it is energized by the normal working current, but, when an interruption or material decrease in said current occurs while the switch-lever F is in its final position, will instantly shift said arm against its back-stop h and break the armature-circuit.

My improved device operates as follows: Assuming the parts of the apparatus to be in the positions shown by full lines in the drawing, to start the motor the main circuit is closed by means of the switch E, thereby closing the branch circuit d through the fields B B of the mot-or and through the winding of magnet K. The switch-lever F is then turned to the left, and upon engaging the first contact g closes the armature-circuit through all the resistance-coils G G, lever F, arm 11 and core 7c of magnet K. The armature now starts slowly, and as its speed increases the lever is moved progressively to the left, cutting out one resistancecoil G after another until it rests in its final position in engagement with contact 9 as indicated by dotted lines, and all the resistance-coils are cut out of the armaturecircuit and the full current passes without external resistance through the armature. In moving the lever F from its initial to its final position the spring L is carried over and past the center pin f, and in the final position of said lever tends to hold it firmly against the stop f in. engagement with the contact g and also to pull the arm II away from the core of magnet K; but said magnet, having been energized at the outset by the closing of the main and field circuits through switch E, holds said arm in contact with its core and maintains the armature-circuit as long as the main and field circuits are unbroken,and the current passing through them is not interrupted or materially weakened. If, however, the main circuit or the field-circuit is broken, either accidentally or, as usual, by the operation of the main switch E, the electromagnet K will gradually lose its excitation as the armature of the motor slows down until its attraction is overcome by the tension of spring L, which will thereupon instantly snap it over against the stop h and break the armature-circuit. If new the main switch E be closed again while the switch-lever F is in its final position, the motor will not start, because the armature-circuit is broken between the pole of magnet K and.

arm II and the attraction of said magnet is not suilicient to restore said arm to its original position against the tension of spring L. To start the motor again under these conditions, it is necessary to turn the switch-lever F back to its initial position against stop f or till it passes the line of arm II, whereupon the spring L, passing to the opposite side of the center of pin f,will snap the arm II against the pole-piece 7c of magnet K, Where it will be held by the attraction of said magnet if the switch E is closed and the field-circuit is supplied with the normal working current. The motor can now be started in the manner hereinbefore explained by turning the switchlever F to the left, which first closes the armaturecircuit with all the resistance included therein and gradually cuts out such resistance until said lever reaches its final position in engagement with the last contact 9 By this means and in the manner above explained it is impossible to pass the full normal current throiilgh the armature-circuit at once before the armature has had time to get in motion and generate a counter electromotiveforce that will prevent injury thereto by the full or normal current.

The switch lever F may be stopped in its initial position on the first contact g with out breaking the armattire-circuit. This is sometimes desirable and does not affect the operation of the automatic switch-arm II, as hereinbefore described.

I have shown and explained my improvements in connection with a shunt wound motor in which the magnet K is preferably placed in the field circ uit (Z, as shown but they are also applicable to a series-wound motor in which the fields and armature of the motor and the winding of said magnet would be arranged in series with each other.

Under certain conditions the series of resistances in the armature may be dispensed with and still the automatic switch-arm employed to advantage in connection with a manually-operated switch-lever, such as F, for opening and closing the armature-circuit.

I claim- 1. In controlling mechanism for electric motors, the combination with a lever adapted to gradually cut out of the armaturc-circuit a series of resistances in starting the motor, of an automatic safety-switch comprising an arm electrically connected with said lever, and movable independently thereof, an electromagnet having its winding in series with the field of the motor and its core or polepiece projecting into the path of said arm, and in electrical connection with the armature-circuit, and a spring arranged to pull said arm out of contact with said pole-piece when said magnet is tie-energized and the switch-lever is in its final position, substantially as and for the purposes set forth.

2. In controlling mechanism for electric motors, the combination with a series of contacts and resistances connected with one of the main conductors of the motor and a switchlever arranged to sweep over said contacts, of an arm electrically connected with said lever and movable independently thereof, an electromagnet having its winding in series with the field of the motor and its core projecting into the path of said arm and electrically connected with the other main conductor of the motor, and a spring connecting said lever and arm and arranged to pull the arm away from the core of the magnet when the lever is in its final position, and to pull it toward said core when the lever is in its initial position, substantially as and for the purposes set forth.

3. In controlling mechanism for electric motors, the combination of a switch-lever controlling resistances in the armature-circuit, of

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an automatic safety-switch consisting of an arm pivoted concentrically with said lever and electrically connected therewith, an electromagnet having its winding in the field-circuit of the motor and its pole projecting into the path of said switch-arm and included in the armature-circuit, and a spring tending to pull said switch-arm away from said magnetpole when the motor is in operation, substantially as and for the purposes set forth.

4. In controlling mechanism for electric motors, the combination with a switch-lever, and a series of contacts and resistances for gradually starting the motor, of an independently-movable switch-arm controlling the ar mature-circuit; an electromagnet arranged to hold said arm in position to maintain said circuit while the normal current passes through the field, and a spring connecting said arm and lever and tending to draw them together when one is turned out of line with the other in either direction, substantially as and for the purposes set forth.

5. In controlling mechanism for electric motors, the combination of a manual switchlever controlling resistances in the armaturecircuit, a concentrically-pivoted switch-arm controlling the armature circuit, stops for limiting the movement of said switch and arm, a spring connecting said switch and arm and tending to draw them together when the lever is turned in either direction out of line with the arm, and an electromagnet arranged to hold said arm against the tension of said spring, in position to maintain the armature-circuit while the normal current passes through the field, substantially as and for the purposes set forth. I

6. In controlling mechanism for electric motors, the combination with a switch-lever for manually controlling the armature-circuit, of an independently-movable switcharm having its winding connected with the motor-circuit, and arranged when energized to hold said arm in position to maintain the circuit, and a spring connecting said arm and lever so as to draw the arm toward the mag net when the switch-lever is in its initial po sition, and away from it when said switchlever is in its final position, substantially as and for the purposes set forth.

7. In controlling mechanism for electric motors, the combination wit-h a switch-lever for successively cutting in and out a series of resistances in circuit with the armature of an independently-movable switch-arm controlling the motor-circuit, an electromagnet having its winding in circuit with the motor and arranged when energized to hold said arm in position to maintain circuit for the motor, and a spring connecting said arm and lever so as to pull the arm toward the magnet when the lever is in its initial position, and away from it when said lever is in its final position, substantially as and for the purposes set forth.

In testimony that I claim the foregoing as my own I afliX my signature in presence of two witnesses.

LUOIUS T. GIBBS.

Witnesses CHAS. L. Goss, ALICE E. Goss. 

